Injecting water into a mixture of fuel and air in an internal combustion engine reduces a working temperature in a combustion chamber of the internal combustion engine. Injecting water into the mixture of a fuel and air also reduces generation of undesirable fuel combustion byproducts such as NOx, carbon monoxide (CO), and various hydrocarbons, thereby improving emissions. A water reservoir may be coupled to the internal combustion engine for injecting water to the combustion chamber. The water from the water reservoir may evaporate rapidly if the water reservoir is in close proximity of the engine due to high temperature. Hence, the water reservoir may be positioned in an area of a vehicle where the temperature is closer to ambient temperature (for example, near a rear trunk, along a side body, or near a fuel tank of the vehicle). However, water in the water reservoir may freeze when ambient temperature is below freezing, interrupting water supply to a water injection system.
Other attempts to address the problem of water freezing in the water reservoir of the water injection system include storing and injecting a blend of water and ethanol from the water reservoir to prevent the water from freezing in the water reservoir. In another approach, the water in the water reservoir may be heated electrically through one or more heater elements coupled to the water reservoir.
However, the inventors herein have recognized potential issues with such systems. As one example, mixing water and ethanol increases cost and complicates the water injection system including complicated air/fuel ratio controls. Additionally, heating the water reservoir electrically increases fuel consumption.
In one example, the issues described above may be addressed by a water injection system, including a first reservoir fluidically coupled to a second reservoir, the second reservoir positioned at a vertically lower plane than the first reservoir, the second reservoir fluidically coupled to a water injector of an engine, a first coolant line in heat exchange relationship with the second reservoir, and a first coolant valve along the first coolant line, upstream of the second reservoir, configured to regulate flow of the coolant through the first coolant line.
In an example, heat exchange relationship between the coolant line and the water in the second reservoir may be by transferring/conducting heat from the coolant through walls of the coolant line to the water inside the second reservoir. The second reservoir may transfer heat to the first reservoir through face-sharing walls of each of the reservoirs. In one example, heat may be transferred to the first reservoir through coolant flowing through a second coolant line in heat exchange relationship with the first reservoir. Heat transfer to the first reservoir may melt ice formed in the first reservoir due to low ambient temperature. The water from the melted ice may drip down from the first reservoir to the fluidically connected second reservoir. Water from the second reservoir may be directed through the water injection line for injection into a combustion chamber of the engine. In another example, the coolant warming the water in the second reservoir may absorb waste heat from a hybrid electric vehicle (HEV) power electronics system. A position of the coolant valve may be regulated based on a temperature of the second reservoir, and based on temperature of coolant at the engine or at the HEV power electronics system.
In this way, the above-described water injection system ensures supply of water for injection into the combustion chamber of the engine even when ambient temperature is below the freezing temperature of the water. In one example, the water injection system reservoir is heated via engine system coolant, and in another example, the water reservoir is heated via HEV power electronics coolant. By doing so, the water injection system may be heated during cold ambient conditions in an energy-efficient manner, ensuring supply of water for injection into the combustion chamber of the engine.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.